A New Silver(I) Aggregate Having an Octagonal Ag 4 S 4 Core Where μ 3 ‐S Bonding Interactions Lead to a Nanotube Assembly that Exhibits Quasiaromaticity

Silver(I) chloride reacts with 2‐mercapto‐3,4,5,6‐tetrahydropyrimidine (StpmH 2 , C 4 H 8 N 2 S) in DMSO with excess triethylamine to give a complex of formula {[Ag 4 Cl 4 (μ 3 ‐StpmH 2 ) 4 ] n } ( 1 ). The product was characterized by elemental analyses, FTIR far‐IR, UV/Vis, and 1 H and 109 Ag NMR spectroscopic techniques. The 109 Ag NMR spectroscopic data of the complexes {[Ag 6 (μ 2 ‐Br) 6 (μ 2 ‐StpmH 2 ) 4 (μ 3 ‐StpmH 2 ) 2 ] n } ( 2 ) and {[Ag 4 (μ 2 ‐StpmH 2 ) 6 ](NO 3 ) 4 } n ( 3 ) are also reported here for comparison. Crystal structure of complex 1 was determined by X‐ray diffraction at 100(1) K. Complex 1 , C 4 H 8 AgClN 2 S, crystallized in the tetragonal system, space group P4cc , a = 15.7761(9) Å, b = 15.7761(9) Å, c = 6.9624(8) Å, V = 1732.8(2) Å 3 , Z = 2. Each metal ion is bonded to one terminal Cl atom and three μ 3 ‐S atoms from three StpmH 2 ligands. Four silver ions are bridged by four sulfur atoms forming an octagonal Ag 4 S 4 core. Each Ag I ion of one core is also bridged to an Ag I ion of another core through a sulfur atom, which forms an infinite nanotube structure. A computational study utilizing the method of nucleus‐independent chemical shifts (NICS) showed that the Ag 4 S 4 core exhibits strong quasiaromaticity at the geometric cage center. To the best of our knowledge, this is the first example of an Ag I cluster that presents quasiaromaticity and stacking interactions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)